Persons working in areas of high ambient noise are commonly provided with sound attenuating equipment in order to protect their hearing. In addition, when such personnel are required to communicate with others in the performance of their duties such sound attenuation equipment is commonly combined with electronic earphones and microphones for permitting two-way voice communication. In environments where impact is not a serious threat, such sound attenuation equipment commonly comprises a pair of ear shells containing earphones supported on the wearer's head by a resilient band extending across the top of the wearer's head. Additionally, a boom microphone is commonly supported on the external surface of one of these ear shells. Typical of such a headphone is the headset manufactured by the David Clark company and sold under various model numbers including H-3330. In environments where impact to the head are a serious danger, sound attenuation equipment may be combined with a helmet structure. Typical of such a helmet is the David Clark company helmet conforming to MIL-H-81735(AS). In that helmet, a cloth cap is fitted with resilient energy-absorbing pads and rigid plastic shells in order to protect the wearer's head from impact. The transverse band joining the two ear shells is secured to the fabric cap by a fabric channel which is snapped in place to surround the band.
Another common approach to the provision of sound attenuation and impact protection for personnel is the incorporation of sound attenuating ear shells within an impact resistant soft helmet such as that exemplified by U.S. Pat. Nos. 3,789,427, 3,786,519 and 3,784,984. In these helmets, a helmet comprised of a fabric mesh which is formed into individual pockets, is provided with a plurality of discreet energy absorbing pads. These pads are inserted into the helmet's pockets in order to provide impact resistance. The helmet structure also contains apertures for the insertion of sound attenuating ear shells containing earphones. Such an aperture in a soft fabric shell helmet is shown in U.S. Pat. No. 3,005,203 as well as numerous other patents including U.S. Pat. No. 3,190,973.
Other methods of securing ear shells to helmet assemblies or to helmet rigging include the use of several straps which are secured to both the ear shell and helmet or rigging. Typical of such a method are U.S. Pat. Nos. 3,335,720 (FIG. 1 - elements 15, 16) and 3,190,973 (FIG. 6 - elements 163). These attachment means, however, fail to provide full freedom of adjustment of the ear shells relative to the wearer's ears. Such adjustment is provided in those patents by conventional sizing of the entire helmet shell.
Prior art sound attenuation and impact resistant helmets of the type discussed above provide reasonable levels of both sound attenuation and resistance. However, prior art designs have severe shortcomings which render them less than entirely satisfactory in use.